Such a vane cell machine is, for example, used as amplification pump before or after a pressure converter in a circuit of a reverse osmosis system. In a reverse osmosis system, water, for example saltwater, is pumped through a membrane and purified or desalinated water is then available on the outlet side of the membrane.
As, in such a machine, the rotor rotates in relation to the stator and a high pressure rules in the work chambers at least once during each rotation, it must be ensured that the vane cell machine is tight towards the inside and towards the outside. An internal leakage would reduce the efficiency. An external leakage is undesirable anyway.
Therefore, the rotor and the side wall must therefore bear on one another with a certain force, in order to keep internal leakages as small as possible. However, this force is not allowed to be too large, as the friction between the side wall and the rotor would thus cause a too large wear.